The female genital tract is a gateway to HIV-1 infection and presents multiple potential anatomically distinct sites for HIV-1 transmission. In pre-menopausal women, fluctuating levels of endogenous reproductive hormones during the menstrual cycle induce morphological, immunological and proteomic changes in all compartments of the genital tract. More than 300 million women regulate fertility by hormonal contraception. Upon reaching menopause, some women begin exogenous hormone treatment to alleviate symptoms of vaginal atrophy. The impact of endogenous/exogenous reproductive hormones on HIV-1 acquisition in women is unknown. The unifying hypothesis of this proposal is that reproductive hormones alter HIV-1 acquisition risk by impacting host factors that regulate HIV-1 entry into the cervicovaginal tract and replication in mucosal CD4+ T lymphocytes and macrophages. We propose the following specific aims. (Aim 1) To quantify the effect of exogenous and endogenous reproductive hormones on HIV-1 susceptibility of the reproductive tract, (Aim 2) To determine whether reproductive hormones alter the mechanisms responsible for HIV-1 transmission through cervicovaginal epithelia, (Aim 3) To quantify the effect of reproductive hormones on HIV-1 dependency factors in the female genital tract. We will assemble a longitudinal cohort of healthy pre- and post-menopausal HIV-1 uninfected women. Subjects will undergo serial cervical and vaginal biopsy during different phases of the menstrual cycle, before/after starting hormonal contraception (high dose oral contraceptives vs. low dose oral contraceptives vs. DMPA) and before/after starting estrogenic creams. Tissues will be placed in organ culture and susceptibility to HIV-1 infection will be quantified and correlated to n vivo conditions of hormonal pressure. Given that the overriding emphasis of this RFA is on whether reproductive health serves as a co-morbid condition for HIV- 1, it is critical to determine whether the hormonal environment that acts as a master regulator of the female reproductive tract truly impacts HIV-1 acquisition.